Developer's Guide

If you make multiple changes and reloads to your homepage, it may
seem said changes do not apply. This is because Smarty caches a
compiled version of the homepage. In order to force Smarty to
recompile templates on every invocation, you must go to "Preferences"
tab, its "Performance" sub-tab, and choose "Yes" for the "Force
recompile" option.
Do not force recompilation on production sites, as it severely
slows everything down!
Using Smarty
Smarty is a PHP template engine, and is used by PrestaShop's theming
system.
It parses TPL files, looking for dynamic elements to replace by their data
equivalents, then displays the generated result. Those dynamic elements
are indicated with curly brackets : { ... }. The programmer may create
new variables and use them in TPL files.
For instance, in our mymodule_page.php, we can create such a variable:
mymodule_page.php
<?php
global $smarty;
include( '../../config/config.inc.php' );
include( '../../header.php' );